LEXINGTON (CBS) – There were extra patrols and rattled nerves but students returned to Lexington High School after a scare Thursday when classes ended early due to threats sent to the school.

Myles Penniman, 20, of Lexington, was arraigned in Concord District Court Friday for allegedly sending the threats in a group text.

A prosecutor said the text sent by Penniman and an unidentified Belmont teenager threatened to shoot teachers and students, and made references to Newtown, Conn., shooter Adam Lanza and the Columbine school shootings in Colorado.

Two Lexington High sophomores included in a group text reported the threats to school officials.

According to the prosecutor, the texts read in part “We are gonna kill the teachers at 3? Lex High is in trouble. U heard O Lanza?Let’s go for the LAB kids first.”

LAB is a class for developmentally challenged students at Lexington High.

Prosecutors said police were notified about the threats by school officials around 11:45 a.m. The threats came from three phone numbers, one of which police traced to a Parker Street home near the high school where Penniman lives with his family, prosecutors said.

WBZ NewsRadio 1030’s Ben Parker reports

Suspect Arraigned In Lexington HS Shooting Threat

According to the prosecutor, Penniman told police he and friends hanging around at his house decided to create a group text to “mess around with kids at Lexington High School.” He allegedly told police they were just joking and wanted to scare them.

Police said the juvenile told them others encouraged him to write about shooting and that once he started writing about shooting “it just kind of went out of control,” the prosecutors said.

A former Lexington High student, Penniman was arrested along with the Belmont teen. The teen was to be arraigned Friday in Framingham Juvenile Court.

A defense attorney representing Penniman said his client has no prior criminal record or history of similar behavior. He is a student at Clark University where he plays basketball.

A judge ordered Penniman held on $5,000 bail. If he makes bail, the judge ordered that he will be under house arrest and must wear a GPS bracelet. He is also barred from texting, using social media or the Internet. He is scheduled to return to court July 21 for a probable cause hearing.

When school officials learned of the possible threat, they enacted emergency response protocols, notified parents and contacted police.

Students said that at about 1 p.m. Thursday an announcement was made over the P.A. system that there was a threat. Students and staff were dismissed early from school and the campus was closed for the day. People at the school were told to leave via a particular street where officers were stationed.